The Campi Flegrei (CF) caldera is one of the most dangerous quiescent volcanic systems in
the world. Its activity mostly resulted in low magnitude explosive eruptions, such as that of the
Monte Nuovo tuff cone that represents the last eruptive event within the caldera (AD 1538).
However, there have been more energetic Plinian events, i.e., the Agnano Monte Spina
eruption (4.1 ky), and very highly-explosive, caldera-forming eruptions, i.e., the Campanian
Ignimbrite eruption (39 ky). Here, we integrate new and literature data on the groundmass
texture and composition of pyroclastic products from the three above eruptions with the aim of
unraveling how volatiles content, degassing mechanisms and crystallization processes
influence magma explosivity and eruption dynamics at CF. Previous studies indicate that the
investigated rocks share similar major element bulk and phenocryst chemistry; also similar is
the water content of their trapped melt inclusions. These observations suggest that the
magmas feeding these eruptions had comparable physico-chemical properties during storage
in the shallow crust. However, our investigations indicate that the studied rocks differ in
texture and composition of the groundmass and viscosity of the related magmas. We ascribe
such differences to the variable style of volatile exsolution and outgassing from the melt,
primarily in response to changes of the rate of magma ascent to the surface. We conclude that
the magma ascent rate was the key-parameter in driving explosive eruptions at CF and we
suggest that this parameter may be influenced by magma/water interaction and/or magma
chamber geometry and replenishment.